1. Field Of The Invention
This invention relates generally to highway culverts, and more particularly, to an inlet collar for use with corrugated pipe, and even more particularly to a collar used in conjunction with corrugated plastic pipe.
2. Description Of The Related Art
This invention is directed to the providing of an inlet collar for improving flow characteristics when used in conjunction with corrugated pipe, with such pipe being, in the preferred embodiment, fabricated from plastic or other similar material well known in the art of pipe fabrication. Tubular steel culverts are well known in the art, as are culverts which utilize concrete pipe.
Where a stream or the runoff from a agricultural field ditch is to pass under a roadway, there are generally two alternatives which may be employed to permit the water to pass under the roadway. The first is the construction of a bridge, which allows full water passage at gravity flow conditions, but can be extremely expensive, especially in applications where the culvert to be crossed is relatively narrow. The other alternative is the use of a culvert system, which tends to pond water at the culvert inlet creating head pressure.
Some culvert systems utilize precast concrete culvert pipe or corrugated metal pipe that extend under the width of the road to pass flow through the roadway embankment. At the opposing ends of the aligned sections may be placed respective pairs of concrete wingwalls, headwalls, or end sections which can assist with the controlling of water flow through the culvert and to prevent the erosion of the ground near the ends of the aligned culvert sections and improve flow characteristics.
Associated with some such culvert systems is a concrete footer on which the aligned culvert sections and wingwalls rest. A contractor can pour cast-in-place wingwalls following the alignment of the precast culvert sections. To retain the wingwall atop a footer, a series of steel reinforcing rods extend upwardly into the upright portion of a wingwall. However, utilization of such systems consumes time and money. For example, utilizing cast-in-place wingwalls typically consumes one to two weeks of additional construction time, with this time associated with the pouring and curing of the four wingwalls. Alternative solutions featuring precast wingwalls are disclosed in U.S. Pat. No. 4,993,872 and in U.S. Pat. No. 5,536,113.
As mentioned above, some culvert systems utilize steel tubing, with U.S. Pat. No. 6,203,245 to Harten disclosing a culvert end guard preferably fabricated from concrete for use with steel pipe to preclude breakage or deformation where the pipe terminates directly adjacent an open culvert of course, the use of concrete pipes would arguably preclude the need for a concrete culvert end guard.
More recently, culvert design has incorporated the use of plastic pipe, especially corrugated plastic pipe. In theory, this change is desirable, since the cost of culvert design using plastic pipe can be a fraction of the cost using concrete pipe. Another way to reduce the cost of the culvert design is to simplify the inlet, for example by eliminating the use of wingwalls, thereby using the end of the pipe as the inlet for the culvert. However, as will be appreciated from the discussion set forth below, the entrance loss coefficients associated with many such existing systems have been too high. Additionally, in order to obtain equivalent flows, plastic pipes have had to be of a greater diameter than concrete pipes, a condition that has often caused the concrete pipe to be chosen due to the perceived benefit of being able to use a smaller diameter pipe.
It is thus apparent that the need exists for an inlet collar for highway culverts which results in a culvert system having an improved entrance loss coefficient, and which is relatively easy and cost effective to fabricate and install in conjunction with plastic pipe, especially corrugated plastic pipe.